1. Field of the Invention
The present invention relates to N,N′-bis(2-cyanoethyl)-1,2-ethylenediamine (hereinafter shortened as BCNEDA), and more particularly to a method for preparing BCNEDA with an improved yield.
2. Description of Related Art
Conventionally, synthesis of BCNEDA uses acetic acid, water, monol-based solvent (e.g., ethanol, isopropanol or methanol) or other promoters as a catalyst for promoting reaction. However, acetic acid can corrode the equipment and other solvents are not helpful to enhance the yield of BCNEDA so there is a need of distillation for product purification.
For example, DE 2446489A1 has in 1976 disclosed a process in which acrylonitrile and ethylenediamine at a molar ratio of 2:1 are used. Acrylonitrile containing therein acetic acid as a catalyst is added into ethylenediamine (EDA) within 2 hours. According to this disclosed process, the obtained product after distillation can give BCNEDA at a yield of 98.1%. Nevertheless, acetic acid used in the process can corrode the equipment and this prevented the process from commercial applications.
As another example, US 2008/0194857A1 discloses a method wherein water is used as a solvent and then acrylonitrile and ethylenediamine at a molar ratio of 2:1 react in the presence of 2-30 wt % of water based on the total reactants to synthesize N,N′-bis(2-cyanoethyl)-1,2-ethylenediamine When the amount of water is 20 wt %, the yield of BCNEDA reaches 93.78%.
Additionally, it is known in the art to use a monol-based solvent (e.g., ethanol, isopropanol or methanol) as a catalyst and to have acrylonitrile and ethylenediamine at a molar ratio of about 2:1 react in the presence of 60-120 wt % of a monol-based solvent based on total reactant, thereby synthesizing BCNEDA. The ethanol solvent provides the most preferred result for it gives a yield of BCNEDA as high as 97.60%.